The present invention relates to a silage cutter having improved efficiency and reliability characteristics.
In the device disclosed in European Patent No. EP 0 506 158 A, the distance between the cutter hinge axle and the part of the gripping devices which is most remote from the hinge axle corresponds to the distance between the hinge axle and the knife. The two cylinders, which are driven for bringing together first and second frame members for a silage cutting operation, are hydraulically controlled via a directional control valve in such a way that, if one cylinder is in advance, the application of pressure to the cylinder will be throttled or interrupted until both cylinders move in synchronism. For this purpose, sensors are provided on both sides of the first frame member, which are connected to the rerouting sides of the directional control valve. An adaptation of the cylinder movements is only effected after a preceding deviation in the movements of the two cylinders; this causes deformations or transverse displacements at the frame members which have to be eliminated afterwards. Further, this adaptation influences the cutting result and causes undesirable high loads in the device. Also, due to the dimensions of the distance, the knife will not neatly cooperate with the gripping devices towards the end of the cutting operation, but instead an undefined cutting condition will occur. The frame members of the disclosed device must be extremely robust, which entails further disadvantages. According to a further embodiment disclosed therein, at least one knife is provided which is adapted to be moved to and fro during the cutting operation and which carries out a sawing movement. However, this knife requires inexpedient dimensions transversely to the cutting direction.
Additional prior art is contained in DE 297 19 753 U, EP 0 779 027 A and in EP 359 482 A.
It is the object of the present invention to provide a silage cutter of the type disclosed above which includes a stationary knife that is forced through the silage and can nevertheless utilize a comparatively light frame. This object is achieved by the silage cutter disclosed and claimed herein.
Since it is guaranteed that the two frame members provided on the two sides of the device will approach each other at exactly the same speed and independently of the reaction force occurring, strong cutting forces can be produced by the present device without any disadvantageous deformation of the frame. Hence, stationary knives which are very flat and thin and which will easily cut through the silage can be used with the present device. Due to the relative distance defined between the pivot axle and the knife on the one hand and between the pivot axle and the most remote point of the gripping device on the other, a defined cutting condition is obtained at the end of the cutting operation. The defined cutting condition is also supported by the cylinders, which are configured to move exactly in synchronism.
When the cylinders of the present invention are connected in series, there will always be a fixed relation between the amount of pressure medium supplied to one cylinder and the amount of pressure medium supplied to the other cylinder. The diameter of one of the cylinders should be smaller than the diameter of the other cylinder so that the pressure medium which is displaced by the piston of one cylinder and which acts on the piston-rod side of the piston of the other cylinder produces identical speeds of the two cylinders.
When the cylinders are connected in parallel, hydraulic means guarantee that the cylinders move in synchronism; thus the cylinders can be dimensioned identically.
It will be expedient to provide hydraulic devices which limit the maximum pressure in each cylinder or the pressure difference between the two cylinders to a set value. This will additionally protect the frame against excessive deformation.
Advantageous kinematic conditions, which are important for high cutting forces and distortion-free cutting, are obtained when the distance between the hinge axle and the articulation point of the cylinders on the first frame member is larger than half the distance between the hinge axle and the knife. It will be expedient when this distance is even larger than two thirds, or even larger than three quarters of the distance between the hinge axle and the knife. The distance between the hinge axle and the articulation point of each cylinder on the first frame member corresponds almost precisely to the distance between the hinge axle and the knife, minus the desired silage cutting depth, i.e. the thickness of a slice of xe2x80x9csilagexe2x80x9d cut out by the knife.
Advantageous kinematic conditions will also be obtained on the second frame member if the distance between the hinge axle and the articulation point of the cylinders on the second frame member is larger then half the distance between the hinge axle and the gripping devices. This distance could even be larger than two thirds, and, if necessary, it could even be larger than three quarters of the distance between the hinge axle and the gripping devices.
The cutting quality will be improved when the first frame member has provided thereon at least one lateral knife which is fixedly attached to the frame member and which extends almost at right angles to the transversely extending main knife and is oriented almost radially to the hinge axle. In this instance, the knife and the two lateral knives are arranged such that they define a U-shape. The lateral knife may have a curved cutting surface.
The cutting edge of the knife and/or of each lateral knife may be straight or it may have a curved shape. Preferably, the cutting edge may have individual parts which extend at a certain angle relative to one another and which define e.g. a knurled or a wavy cutting edge. Good cutting results can be achieved by knives and lateral knives, respectively, in the case of which the distance between forwardly extending portions of the cutting edge is smaller than 8 cm, or even smaller than 6 cm, or, even better, smaller than 4 cm.
The knife may be a metal plate on which the cutting edge is defined by an edge-side bevel of the plate. The bevel should be located on the side facing away from the hinge axle so as to achieve a good cutting quality.
The second frame member is provided with one or with a plurality of cutting devices which are intended to cooperate with the knife and/or the lateral knives of the first frame member. When the cutting edge of each knife moves against or almost against one of these cutting devices at the end of the cutting operation, the silage will be cut neatly.
At one edge of the cutting device, the cutting edge of the knife or of the lateral knife will move in such a way that a scissorlike cutting movement or a drawing cut will be obtained. The cutting device may be provided with an immersion groove for the cutting edge of the knife and of the lateral knives, respectively; the cutting edges need not touch the bottom of the groove, since a good cut is already effected at the edges. The gripping devices define a kind of loading flap and have a platelike member provided with a sharp edge or teeth which is/are adapted to be pressed into the silage block. It will be expedient to implement the platelike member such that it does not have any openings so that the cut-out silage will drop on the platelike member for being then transferred in its entirety to a mixing chamber of the silage cutter.
When the differential distance mentioned at the beginning is at least 5 cm, or even better 15 cm, a substantial part of the gripping device will still be located in the uncut silage when the cutting operation has almost been finished. In addition, the knife and the later knives cooperate very effectively with the gripping devices.
Even if comparatively strong cutting forces are generated by the hydraulic cylinders, the guide mechanisms will assist in the formation of a neat cut because the frame members are guided along one another and will not move parallel to the hinge axle nor deform.
A stop of the guide mechanism permits an exact adjustment of the end of the movement of the knives. At the end of a cutting operation, the knives, as soon as the stop becomes effective, have carried out a movement corresponding to almost their whole effective length up to a point located very close to the cutting devices so that the whole silage located below the knife is neatly cut through.
Part of the mixing chamber used for depositing the cut-out silage is defined by the second frame member. It will be expedient when the second frame member is tiltably secured to the mixing chamber by means of a hinge so that the cut-out silage can be deposited in the mixing chamber by tilting the second frame member. The mixing chamber may have provided therein a mixing device and/or other devices for treating the silage.
Alternatively, the second frame member can be connected to the mixing chamber in a more or less stationary manner and define the bottom of the mixing chamber, whereas the first frame member is equipped with a loading flap which is pivotable on arms, the knife being secured to the edge of the loading flap. For connecting the loading flap to the first frame member, a hinge or a sliding mechanism can be used. The second frame member can define an approximately flat extension of the bottom of the mixing chamber on which the cut-out silage is deposited.
When traveling, the silage cutter is supported by ground support wheels. The silage cutter can be adjusted approximately vertically relative to the wheels by means of a suitable adjustment device. In this way, it is possible to lower the gripping devices until they touch the ground and to push them along the ground up to and below the silage to be cut out. Losses will be avoided in this way. For transporting the cut-out silage, the silage cutter can be raised on the wheels so as to be easily movable.
Making use of the fact that the second frame member is pivotable on said mixing chamber with the aid of two hydraulic cylinders, if the cut-out silage is transferred to the mixing chamber, control valves, e.g. check valves, should be provided in pressure medium supply conduits of these cylinders so that the length of the two cylinders and, consequently, the respective pivotal position of the second frame member can be fixed in relation to the mixing chamber, at least temporarily.
A precise synchronous movement of the two cylinders, which have to produce the cutting forces and which are connected in parallel, is achieved by means of a hydraulic flow divider configured to supply identical pressure medium flows to the two cylinders, irrespective of the extent to which the counter forces at the two cylinders may perhaps differ from one another. In comparison with a directional control valve which is only actuated in response to a deviation from a condition of synchronous movement so as to eliminate said deviation, the flow divider has the advantage that there will be no deviation from a synchronous movement because, if the counter pressure at one cylinder increases, the flow divider will supply this cylinder, irrespective of the increasing counter pressure, with the same amount of pressure medium as the other cylinder so that a relative advance will be excluded.
To prevent the silage cutter from being damaged, if an obstacle would become effective on one side of the silage cutter, or some other obstruction should occur, pressure-limiting valves are provided which limit the maximum pressure in each cylinder and/or the maximum differential pressure between the cylinders and which will therefore respond automatically to an emergency situation.
Also, if the cylinders are connected in series, both cylinders should be supervised by pilot-controlled pressure-limit valves defining equalizing valves so as to reduce excessive pressure and avoid damage in the event of an emergency situation.
It is part of the present invention that a silage cutter is controlled in such a way that a stationary knife on the first frame member is forced through the silage until said silage is finally cut through completely against gripping devices of the second frame member. The cutting forces are produced by two spaced cylinders which are controlled such that they always have the same length, whereby a distortion of the frame of the silage cutter or deformations is avoided. For this purpose, the two cylinders are hydraulically controlled in such a way that, irrespective of their individual counter pressure, they will be moved at the same speed and will always correspond in length to one another.
Since in cases where the cylinders are connected in parallel and pressure medium flows are apportioned to the cylinders via the flow divider, a 100% distribution cannot be guaranteed due to production-dependent and function-dependent tolerances, especially in the case of cylinder strokes of up to 200 mm and more, it may be expedient to associate, during silage cutting, a downstream compensating control valve with the flow divider, the compensating control valve throttling, if necessary up to complete blockage, the flow to the respective cylinder operating against the lower counter pressure on the supply side. This permits, at least during silage cutting, a largely ideal synchronous movement.
Alternatively, the cylinder operating against the lower counter pressure during silage cutting can intentionally be biased or decelerated on its discharge side; this is achieved either via a brake valve adjusted by a differential-pressure compensating control valve and located in the blocking conduit of the respective cylinder that leads to the common discharge conduit, or by a compensating control valve which is directly connected to the discharge conduits, or by biased control valves which are arranged directly in the discharge conduits and which are controlled crosswise from the operating conduits. Interventions on the discharge sides of the cylinders have, in the case of synchronous operation control processes, the advantage that only small pressure medium volumes or comparatively low pressures have to be governed.